Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$164.40	5.425%	$173.3187	$173.32	$173.30	$173.30
Purchase #2	$222.66	10.705%	$246.4958	$246.50	$246.50	$246.50
Purchase #3	$39.37	4.479%	$41.1334	$41.13	$41.15	$41.10
Purchase #4	$100.26	8.382%	$108.6638	$108.66	$108.65	$108.70
Purchase #5	$208.94	7.136%	$223.85	$223.85	$223.85	$223.90
Purchase #6	$117.25	12.526%	$131.9367	$131.94	$131.95	$131.90
Purchase #7	$99.69	9.637%	$109.2971	$109.30	$109.30	$109.30
7 purchase totals =	$952.57		$1,034.6955	$1,034.70	$1,034.70	$1,034.70